Application development - IBM - AS/400

CICS/400 offers a number of facilities to assist the application program developer:

  1. Application programming interface
  2. The CICS/400 application programming interface (API) includes virtually all the commands and functions that you would expect to have in a CICS mainframe system. The only items missing are those that are not applicable to the OS/400 architecture, such as standard and full function BMS, support for terminals other than 3270 and 5250 devices, acquisition of storage above the 16MB line, and program loading. All other standard CICS API commands are available for CICS/400.

  3. Source language translator
  4. All CICS/400 application programs must be written in either AD/Cycle®COBOL/400 or ILE C. The translation process converts the embedded EXEC CICS commands into either COBOL/400 or C statements and program calls to the appropriate CICS/400 support modules. An OS/400 precompiler is used to invoke the translator. The input to this procedure is the COBOL/400 or C code with embedded EXEC CICS commands. After successful translation, the resulting output is compiled by the appropriate language compiler.

  5. Map translation
  6. CICS/400 includes a translator for maps created using BMS. An OS/400 CL command is used to create the object versions of your maps ready for use in your programs. A COBOL copybook or C header file is also created.

  7. CICS/400 system programming commands
  8. CICS/400 includes a special group of commands that are used for monitoring the system, for changing certain parameters with the CICS/400 control region, and for resource administration. These commands, which duplicate many of the functions of the supplied transaction CEMT, are executed from within the application program.

  9. Application testing

    There are four supplied transactions that are useful to application programmers for testing applications:

    The temporary storage browse (CEBR) transaction allows authorized users to work in real time with temporary storage queues. You can also use CEBR to transfer a transient data queue to temporary storage in order to look at its contents, and to transfer the data back to a transient data queue.

    The execution diagnostic facility (CEDF) intercepts EXEC CICS commands at various points within an application program, allowing you to see what is happening. Screens sent by the application program are preserved, so that you can converse with the application program during testing.

    The command-level interpreter (CECI) allows you check the syntax of EXECCICS commands and to run the commands interactively on a terminal screen. CECI interacts with your test system to allow you to create and delete test data and temporary storage queues, or deliberately to introduce wrong data to test out error logic.

    The CICS routing transaction CRTE allows you to pass through to a remote system to verify the creation of temporary storage queues,check connections,and so on.

  10. Problem determination

    You can dump runtime storage areas, both within a shell environment and within the control region.

    OS/400 dump facilities support the EXEC CICS DUMP TRANSACTION command. COBOL transaction dumps are provided by the COBOL/400 dump format and print program. C transaction dumps are handled by the DMPJOB CL command, which is also used to support the control region dump requested by the CEMT PERFORM SNAP command.

    System dumps,including unformatted trace and control block information, are provided as part of the First Failure Data Capture process that results from CICS/400 internal errors.

    CICS/400 trace

    You can trace runtime areas, both within a shell environment and within the control region. If CICS/400 internal trace is active, each execution of an EXEC CICS command results in trace entries being written to an in-memory trace table. Alternatively, these trace table entries are written to an OS/400 user space object. The trace entries can then be formatted and printed by an offline trace print utility program, initiated by a PRTCICSTRC CL command, supplied within CICS/400. In addition, application programmers can invoke CICS/400 tracing from within their programs.

    Recovery and restart

    CICS/400 resources can be recoverable if recovery information is recorded by the OS/400 commitment control and journaling facilities. Such resources are recovered using standard OS/400 functions.

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